Stabilizing Wet Natural History Collections
Facts about natural history collections
- It is as important to preserve specimen labels (which are often loose) as it is to preserve the specimens themselves. Keep specimens associated with their labels. Transfer data to fresh paper if necessary.
- There are many sources of toxic materials in natural history collections. Wear appropriate PPE when handling natural history specimens. Take advice about the presence of:
- Toxic mineral species
- Radioactivity (some minerals and fossils)
- Asbestos used in fossil fills
- Pesticides – DDT, arsenic, etc. on zoological specimens or DDT or mercury compounds on botanical specimens
- Fluid collections – formaldehyde
What to expect when NH collections get wet
- Most minerals species are stable in water, but many are not: some minerals are water soluble, while others may convert to their hydrated form or corrode.
- Generally fossil specimens are fairly stable in water. However, unstable matrices such as microcrystalline iron sulfide will deteriorate rapidly in damp conditions, and matrices such as shale may swell. Restored areas and joins may be softened. Sub-fossil bone may crack.
- Herbarium specimens stuck with water-soluble adhesives may come loose from herbarium sheets.
- Most study skins are untanned or semi-tanned products and are extremely vulnerable to damage from wetting. Skins will lost strength and distort when wet, and with prolonged soaking will gelatinize. Skins with natural fillings (cotton, flax, or wood shavings) will hold moisture and are more difficult to dry than polyester fiber-filled skins.
General stabilization and drying information
- Always keep labels with specimens.
- Unstable specimens that may suffer delamination or dissociation of parts on drying should be secured with cloth tape or string, or contained in a tray, during the drying process.
- For minerals, fossils, and bone, air drying is usually the preferred method. Dry in place, within cabinets or within drawers, where possible, to lessen handling and potential for label loss. Use fans and dehumidifiers to speed drying. Dry sensitive materials slowly. Do not freeze, or freeze dry, fossils, minerals, or bone.
- Herbarium specimens can be treated essentially like paper. Avoid direct handling; use a support when lifting herbarium sheets. If mold is threatened, sheets can be frozen, although damage may occur to brittle plants. Interleave sheets with silicone release paper or freezer paper, enclose in polyethylene, and freeze in stacks.
- Study skins: Avoid direct handling of wet study skins, which will be greatly weakened, as they are easily distorted. Allow them to dry in their storage trays if at all possible. Controlled air drying is preferred. If dealing with large quantities, consider desiccant air drying. Specimens may be frozen if necessary to prevent mold growth.
- Taxidermy mounts should be air dried as soon as possible. Sutures can be reinforced with wrappings of gauze bandage. Generally, do not freeze.
Natural History Salvage Priorities
In all NH collections, the overarching priorities, no matter what their condition include:
- Type specimens
- Specimens of rare, endangered, or extinct specimens
- Voucher specimens for specific research projects
- Figured specimens
- Specimens with historic value
After that, priorities based on vulnerabilities are as follows:
- Mineral Collections Salvage Priorities:
- native iron
- Fossil Collections Salvage Priorities:
- pyritic (iron sulfide) fossils
- Fossils in shale
- sub-fossil (i.e., not fully fossilized) bone
- mammoth tusks and teeth
- mounted specimens with iron armatures
- Botanical Collections Salvage Priorities:
- Specimens on acidic paper or paper treated with mercuric chloride
- Specimens adhered with water-soluble adhesives (many!)
- Zoological Collections Salvage Priorities:
- Study skins with natural stuffings (vs. polyester fiber)